Brake operated signal system



Ahg. 11, 1942. .1. c. D. JENSEN 2,292,373

BRAKE OPERATED SIGNAL SYSTEM i'ili d Feb; 28, 1939 2 Sheets-Sheet l [/5404 John 6. 0. Jensen 11, 1942. J. c. D. JENSEN BRAKE OPERATED SIGNALSYSTEM Filed Feb. 28, 1939 2 Sheets-SheetJ-Z NEY I N VENTOR John C 0.fnsen BY ye i 7 II n 59 a as Patented Aug. 11, 1942 UNITED STATES iATENT ()FFICE BRAKE OPERATED SIGNAL SYSTEM Application February 28, 139, Serial No. 259,015

(Cl. 2ii0--82) 5 Claims.

The present invention relates to a hydraulic brake system and moreparticularly to the location of the switch means of a signaling systemwhich is controlled by said brake system.

The use of the master cylinder of an automotive hydraulic brake systemto control a stop light signal is well known. However, in such knownarrangements the switch means is generally operated hydraulically by thepressure created in the liquid of the brake system and is generallyconnected to the high pressure side of the master cylinder. As a result,one more possible source of failure is added to the brake system becausecertain of the several parts of said switch means are placed under veryhigh pressure whenever the brakes are applied and often become fatiguedand disrupted in time. In addition, the hydraulic liquid generally usedhas a highly corrosive action which also in time eats away oraccelerates the failure of the switch parts. The serious consequences ofthe failure of such a stop light switch on the pressure side of themaster cylinder are obvious.

The primary object of the present invention is the provision of a signalswitch means which is operated by a hydraulic brake system and whichcontrols the signal but which does not jeopardize the reliability of thebrake system.

Another object of the invention is the provision of a signal switchmeans which causes energization of a signal whenever a hydraulic brakesystem is operated but which is actuated mechanically by the mastercylinder of said brake system and which is operated from the lowpressure side of said cylinder.

A further object is the provision of a normally closed signal switchmeans which is open when the hydraulic brake system is inoperative butwhich is associated with the low pressure side of the master cylinder soas to be closed when the brake system becomes operative.

Still another object is the provision of a signal switch means which isoperated mechanically by the piston member of the master cylinder andwhich is located so that failure or disruption of said switch means doesnot affect or destroy the operativeness of the hydraulic brake system.

A still further object of the invention is the provision of a normallyclosed signal switch means which is located on the low pressure side ofthe master cylinder and which is opened mechanically by the pistonmember in said cylinder when the braking pressure is released.

Other and further objects of the invention will be apparent or suggestedto those skilled in the art by the disclosure which follows.

The aforementioned and other objects of the invention are realized in ahydraulic brake system including a closed cylinder which is divided intoa high pressure and low pressure chamber by a piston member, and whereina signal switch means is associated with said low pressure chamber and/or said piston member so that said switch is closed when the brakesystem is operative and is opened when said brake system is inoperative.

Reference is hereby made to the accompanying drawings wherein similarreference characters designate similar elements and wherein:

Fig. 1 is a longitudinal section of the master cylinder of a hydraulicbrake system showing the preferred arrangement of the signal switch withrespect thereto according to the invention.

Fig. 2 is a similar but fragmentary cross-section to enlarged scale andalso includes a crosssection of the signal switch.

Fig. 3 is a transverse cross-section of said switch taken on the line 33of Fig. 2.

Fig. 4 is a longitudinal section through a modified form of the signalswitch.

Fig. 5 is also a longitudinal section of the master cylinder showing theswitch means mechanically operated by the piston rod of the pistonmember.

Fig. 6 is a longitudinal fragmentary crosssection to enlarged scale ofthe master cylinder showing the switch means located in one sidethereof.

Fig. '7 is an end View of the switch means modified for'such location onthe side of said master cylinder.

Fig. 8 is a fragmentary cross-section of the master cylinder and asimplified form of switch means operated by the piston rod of the pistonmember.

In the illustrated embodiments of the invention the arrangement of thesignal switch means is shown in connection with one standard orcommercial type of hydraulic brake system, however, it is to beunderstood that the features of the invention may be employed to equaladvantage in other known types of hydraulic brake systems.

The hydraulic brake system as shown is mounted upon a frame bracket itand basically comprises a pedal assembly and a master cylinder assembly.

The pedal assembly may comprises a pedal arm H intermediately pivoted ona shaft 12. Said pedal arm I! has a foot pad [3 on one end thereof andhas on the other end thereof a stud l4 which is connected by a coilspring |5 to a stud |6 on frame bracket I0. As a result the pedal arm IIand foot pad |3 are resiliently urged in a clock-wise direction.

The master cylinder assembly may comprise a cylinder and reservoirhousing I! which is provided with a cylinder bore l8 and with a liquidreservoir I9 and which has an intermediate wall 20. Said housing I1 isattached at one end to frame bracket I by means of bolts 2| and has acap 22 threaded into the top of housing H to permit replenishment of theliquid supply. Housing I! may also have an integral collar 23 which hasan internally threaded bore 24 and which is provided with an externalannular groove 25. The frame bracket I0 is provided with a hole 26 whichis somewhat larger in diameter than collar 23. A rubber sleeve 21 havingan internal rim 28 has one end thereof clamped between said collar 23and within the hole 26 of frame bracket H] with rim 28 within groove 25.

A cylinder head 29 is threaded into threaded bore 24 and is providedwith a central opening through which extends the piston rod 30 of apiston member. One end of piston rod 30 is pivotally connected to pedalarm II b a pin 3| and said piston rod 30 is intermediately provided witha portion 32 of reduced diameter, see Fig. 2, to which the re-entrantend 33 of rubber sleeve 21 is attached by means of a spring retainer 34.

The piston member also comprises a piston 35 having annular end flanges36 and 31 which are substantially equal in diameter to the diameter ofthe cylinder bore l8. Said piston 35 is preferably arranged as shown inFig. 2 and comprises an inner piston sleeve 38 carrying the flange 36and provided internally with a flared piston rod seat 39 for receivingthe end of piston rod 30 which extends through the central opening incylinder head 29. An outer piston sleeve 40 makes a press fit with innersleeve 38 and clamps a Washer 4| and rubber U-sectioned piston ring 42therebetween. A cup-shaped rubber piston ring 43 is pressed against theinner end of piston 35 by one end of a helically coiled spring 44 whichhas its other end bearing on a seat 45 at one end of cylinder bore l8.Consequently, the piston 35 is normally returned to a definite orpredetermined position with its flange 36 abutting against cylinder head29 when the pressure on the pedal assembly and in the hydraulic liquidis released.

The liquid distribution system is of a standard or well known type andmay include individual hydraulically operated brake cylinders, notshown, but connected to the master cylinder by a pipe 46 attached to acollar 41 which is provided with a hole 48 and which is fastened to theother end of cylinder and reservoir housing I'1 by a bolt 49 providedwith a central bore 50.

An inlet port and an equalizing port 52 are provided in intermediatewall 20. The inlet port 5| has a restricted portion entering thecylinder bore |8 just ahead of the piston ring 43 when the piston 35 isin the normal or predetermined position and permits the liquid in themaster cylinder to be replenished by liquid from the reservoir l9 tocompensate for liquid accidentally lost from the master cylinder or inthe distribution system. As soon as the pedal assembly is operated byexerting foot pressure on foot pad IS, the piston ring 43 movesforwardly covers inlet port 5| and a hydraulic pressure is createdwithin the high pressure chamber of the master cylinder and isdistributed throughout the brake system.

The space between the annular flanges 36 and 31 and particularly thespace behind the piston 35 after displacement thereof are under littleif any positive pressure. Any of the hydraulic liquid that passes thepiston ring 43 is returned in a known manner through the equalizing port52 to the reservoir l9 when the piston 35 is returned to its normal orpredetermined position by the spring 44. The piston ring 42 will preventany appreciable amount of liquid passing the flange 36. Hence, thannular space between flanges 36 and 31 or the space behind the piston35 after its displacement, or both, constitute a low pressure chamberwithin the master cylinder.

The signal system comprises a signal, a source of energy and a switchmeans. The signal is preferably of the visual type, such as a stop-light53, and has one side connected through the source of energy or battery54 to ground. The other side of the stop-light 53 is connected throughone leg 55 of a wire 56 to one post 5'! of a switch means, designatedgenerally as 58, While the other post 59 of said switch means isconnected through the other leg 60 of wire 56 to ground.

Three forms of a suitable switch means are disclosed herein, although itis to be understood that any form of switch assembly which includes apair of contacts and an operating member associated with the lowpressure side of the master cylinder and actuated by the return of thepiston in the master cylinder to normal or predetermined position isWithin the scope of the invention.

One form of switch means is shown in Figs. 2 and 3 and comprises acup-shaped member 6| having on one end an inturned flange 62 and at theother end a shoulder 63 and a threaded nipple 64. The cup member 6| isenclosed by a cover 65 of insulating material which is preferablymoldable. Said cover 65 has a shoulder 66 engaged by flange 62 and isprovided with a switch recess 61 and with a bore 68. Said posts 51 and59 each have respective portions 69 and 10 of reduced diameter andhaving knurled sections and all of which are imbedded or moulded incover 65.

A pair of contacts, preferably normally closed, are placed within switchrecess 61, one contact having a base flange 1| attached to portion 69 ofpost 51 by a rivet 12 and having a contact arm l3 carrying a contactpoint 14, the other contact having a flange 15 fastened to portion 10 bya rivet 1S and having a contact arm 11 carrying a contact point 18. Acoil spring 19 is placed within bore 68 and normally presses contact arm11 and contact point 18 into engagement with contact point 14.

A rigid disk 89, preferably of steel, is provided with a central hole 8|and covers the switch recess 61. A washer 82 of dielectric material maybe interposed between said disk 89 and the annular rim of cover 65. Aconcave flexible flanged cap 83 is placed over disk 60 and is preferablycomposed of phosphor bronze. A second dielectric washer 84 and acompressible dielectric or rubber washer 85 are placed between cap 83and the adjacent shoulder of cup member 6|. A hard ball 86, such as aball bearing, is movable within the hole 8| of disk and transmits themovement or flexure of cap 83 to contact arm 11 to disengage contactpoint 18 from contact point 14. The spring 19 oppose such movement,holds ball 86 against cap 83 and normally closes contact points I4 andI8.

An operating member of the switch means normally may extend into themaster cylinder on the low pressure side thereof and is located so as tobe operated by the piston member when it is returned to its normal or apredetermined position. Such operating member may be of the compensatingtype as shown in Figs. 2 and 6 or may be of the direct type shown inFig. 4.

The compensating type of operating member may comprise, see Fig. 2, asleeve 8'! which is movably mounted within nipple 64, which has a collar88, and which is provided with a bore 89. A plunger 98 extends into bore89 and has a head 9| bearing against the concave flexible cap 83. A coilspring 92 is placed within bore 89 and tends to eject the plunger 99therefrom. Said spring 92 is stronger than the combined and oppositeresilient effect of cap 83, contact arm I! and spring I9 so that inwardmovement of sleeve 8! is immediately transmitted through spring 92 andplunger 99 to the cap 83, ball 86 and contact arm I? resulting incompression of spring 19. After the contact point I4 and I8 have beenopened and cap 83 has been flexed against disk 80, any further inwardmovement of sleeve 81 will merely cause compression of spring 92. Thusany damage to or excessive pressure upon the internal parts of theswitch means are avoided. The spring I9 and 92 may also be proportionedor arranged so that the aforementioned compensation will occur soonafter the contacts are opened and whether or not the rigid disk 88intercedes.

The direct type of operating member, see Fig. 4, may comprise a plunger93 extending at one end out of nipple 64 and having at its other end ahead 94 which bears against the flexible cap 83. The nipple 84 may alsobe provided with a recess 95 within which is located a spring 98 whichencircles plunger 93 and a collar 9! bearing against a pin 93 on plunger93. As a result, plunger 93 is normally urged by spring 96 to extend outof nipple 64.

The switch means may be optionally modified by mounting one contactpoint 99 on a contact arm E88 by a rivet I9! which is driven intoportion 89 of post 51 and by mounting contact point I82 on a spring armI93 which is fastened to portion 78 of post 59 by a rivet I84. Also thedisk 89 may be provided with a flared opening I in which may move a pinI98 having a tapered head I81. The spring I9 holds arm I93 with contactpoint I82 against contact point 99. When the plunger 93 is movedinwardly, as by the piston member of the master cylinder, the cap 83 isflexed, pin I98 and spring arm I83 are moved to open the contact points99 and I02.

The axial displacement of plunger 93 is limited by the concavity of cap83 or distance through which said cap 83 is flexed to abut against disk89. Since the distance which plunger 93 extends beyond the inner face ofcylinder head 29 is greater than such axial displacement of said plunger93, the normal return of the piston 35 is stopped in a predeterminedposition by said plunger 93 and disk 80.

The primary feature of the invention is the 10- cation of the switchmeans so that its operating member is mechanically actuated from the lowpressure side of the master cylinder of the hydraulic brake system andby the piston member thereof. Several possible locations of the switchmeans and its operating member are disclosed herein. The switch meansmay be mounted upon the master cylinder with the operating member ofsaid switch means projecting or extending into the path of the pistonmember so that said operating member is moved to open the switch meanswhen the piston member returns to its normal or a predeterminedposition.

One arrangement of the switch means is to thread its nipple 64 into athreaded bore in the cylinder head 29 with the shoulder 83 abuttingagainst the outer surface of said cylinder head 29. In this way accuratelocation of the operating member with respect to the piston member maybe obtained under standard manufacturing conditions. The cylinder head29 is of known thickness and the projecting ends of sleeve 8'! andplunger 93 are spaced from shoulder 63 so as to extend into the lowpressure chamber of the hydraulic cylinder the desired distance and sothat said sleeve 81 or plunger 93 may be axially displaced sufficientlyto open the contact points 14 and E8 or 99 and I92.

Another arrangement of the switch means according to the invention issuch that the operating member of the switch means is operated by thepiston rod of the piston member. For accomplishment of this form of theinvention the construction of the master cylinder may be as alreadydescribed or may be varied as shown in Fig. 5. For instance, thecylinder and reservoir housing Il has an integral collar I98 which isprovided with a groove I99 and with an opening of slightly largerdiameter than cylinder bore I8 so that a shoulder I I8 is formed at oneend of said cylinder bore l8.

The piston member comprises a piston I I I and a piston rod II2. Saidpiston III carries a plurality of piston rings H3 and a rubber cup H4 ispressed against the inner end of piston I ll by the helical spring 44.The piston rod I I2 has one end attached to the outer end of piston IIIas by a threaded connection and a lock nut I I5 and the other end ofpiston rod II2 is connected by a pin 3! to the pedal arm I I. The lowpressure end of the cylinder bore I8 is enclosed by a disk II8 which isheld against shoulder III] by a spring retainer II'I within the grooveI89 and which is provided with a central opening through which thepiston rod I I2 extends.

The rubber sleeve 21 has at one end a re-en trant portion which grips areduced portion II8 of piston rod I I2 and has at its other end an outerhead II9 which is clamped between the frame bracket I9 and said collarI98.

The switch means 58 may be constructed internally either as shown inFig. 2 or Fig. 4 or in any other suitable manner and includes a threadednipple 64 and a normally projecting operating member I29. Said switchmeans 58 has one post 51 connected to ground through stop light 53 andbattery 54 and has its other post 59 connected directly to ground. Theswitch means is also mounted in a position adjacent the piston rod II2such as by attachment to a convenient part of the vehicle or preferablyby having its nipple 84 threaded into one end of a bracket I2I which hasits other end fastened to frame bracket I8 by one of bolts 2I.

The piston rod II2 carries a projection I22 which is preferably formedintegral with said rod II2 but may be detachably and/or adjustablyfastened thereto. Projection I22 engages the operating member I28 ofswitch means 58 when the piston member is returned to its normalposition by the spring 44 upon release of pressure from the pedalassembly. Such return of projection I22 also moves said operating memberI20 to open the contacts within switch means 53 and de-energize thesignal circuit. If the switch means 58 is of the direct type shown inFig. 4, the final position of the piston member will be determined bythe plunger 93 and disk 83. If the switch means is of the compensatingtype shown in Fig. 2, then the final position of the piston member willbe determined by engagement of the projection I22 either with nipple I34of the switch means or with the bracket I2I As a result of sucharrangement of the invention, the switch means is not subjected even toa low hydraulic pressure and need not be fluid tight so that theinternal construction of the switch means may be considerably simplifiedand may also be provided as illustrated in Fig. 8. The construction ofthe master cylinder and piston member need not be changed in any respectfor the adaptations of the invention shown in Figs. 5 and 8 which isquite advantageous at all times but especially when the signal system isapplied to an existing hydraulic brake system.

As shown in Fig. 8, the master cylinder comprises, as before, thecylinder housing I1 which is mounted upon the frame bracket Ill, anintermediate Wall 20, and an integral collar I08 which is provided witha groove I09 and with an opening of slightly larger diameter thancylinder bore I8 to form a shoulder III against which the disk H6 isheld by a spring retainer II1. Also the piston member may again comprisea piston 35 having flanges 35 and 31 and provided with. a divergingpiston rod seat 33 for receiving the ballshaped end of piston rod 38which extends through a central opening in disk I I6. A pair of flexiblepiston rings 42 and 43 are also mounted adjacent the flanges 36 and 31of said piston 35.

In this form of the invention, see Fig. 8, the switch means comprises acup-shaped housing I36 of molded insulating material and which may beattached to the disk II6 by a pair of screws I31. A pair of contactmembers are mounted on housing I36 and may comprise a contact arm I38fastened by a bolt I39 to a side wall of housing I36, and a contact armI43 fastened by a bolt I4I to the opposite side wall of housing I36. Oneleg I42 of a wire I43 is attached to bolt I39 by a nut I44 while theother leg I45 of wire I43 is attached to bolt MI by a nut I46. The legsI42 and I45 of wire I43 may be attached to the signal system in themanner already disclosed.

The signal circuit is completed by a contact member mounted directlyupon the piston rod 30 of the piston member and located to interrupt thecircuit when the piston member and piston rod 30 are in a normaldefinite position, in this case determined by the location of disk IISand said signal circuit is completed immediately when the piston rod 30is moved to create a hydraulic braking pressure in the master cylinder.Such a contact member may comprise an insulating bushing I41 pressedonto piston rod 38 and maintained in the desired position thereon byengagement with a longitudinally knurled section I48 of piston rod 30and may also comprise a contact sleeve I49 which is preferably mouldedinto bushing I41.

The switch means so located may be protected from dirt and damage by theconventional rubber sleeve 21 which may have at one end an outer beadII9 clamped between collar I08 and frame bracket II], which may have atthe other end a reentrant portion for tightly gripping piston rod 30,and which is provided with an opening through which wire I43 may extend.Such protection by sleeve 21 eliminates the necessity of covering theopen end of cup-shaped housing I36 although if desirable a suitablecover may be provided for said open end of housing I36.

According to still another realization of the invention, the switchmeans 58 may be mounted one. side wall of the master cylinder fromwhence its operating member extends into the low pressure chamber of themaster cylinder and may also carry an abutment for stopping the returnmovement of the piston. As illustrated in Fig. 6 the master cylinder maybe constructed the same as shown in Fig. 5 except that the housing I1 isprovided in its side wall with an opening I23 and preferably has anexternal boss I24 which is provided with a recess I25.

The internal construction of the switch means may be the same as thatshown in Fig. 2 or Fig. 4. It is desirable, however, to modify theswitch housing and the projecting end of the operating member. Theswitch housing I26 has a flat end wall I21 for abutting against the faceof said boss I24, has a plurality of lugs I28 through which screws I29are threaded into boss I24, and has an unthreaded nipple I38 extendinginto said opening I23. Said nipple I30 may carry an abutment I3I whichextends into the low pressure chamber of the master cylinder to limitthe return movement of the piston III and is pro vided with a squarehole I32 within which a square operating member I33 may move. Saidoperating member I33 has a rim I34 on its inner end and has its other orprojecting end I35 beveled, tapered or otherwise formed so that thereturn of piston I II to its normal or inoperative position will movesaid operating member I33 toward said switch means. Such movement ofoperating member I33 will exert a pressure on spring 92, plunger 90, cap83, ball 86 and spring arm 11 and will overcome the effort exerted byspring 19 and spring arm 11 so that contact points 14 and 18 will beseparated and the signal circuit will be opened. It is, of course,understood that the cylinder head or other arrangement may be made tolimit the return movement of the piston in the master cylinder since themember I33 is not further retracted by additional movement of pistonIII, however, it is deemed more convenient to provide such abutment onthe nipple of the switch housing so that the final position of thepiston III is in definite and accurate relation to the operating memberI33.

Since many other variations and modifications of the invention arepossible, the present disclosure is to be constructed in an illustrativesense. The scope of the invention is defined by the claims which follow.

What I claim is:

1. In a hydraulic brake system, the combination with a closed cylinderadapted to contain a liquid, and a piston within said cylinder anddividing the interior thereof into a high pressure chamber and a lowpressure chamber, of a switch means mounted upon said cylinder andcomprising a pair of contacts which are closed when said piston is movedto create a braking pressure in said high pressure chamber, and anoperating member extending into the low pressure chamber of saidcylinder and mechanically actuated by said piston to open said contactswhen the braking pressure is relieved from said high pressure chamber.

2. In a hydraulic brake system, the combination with a closed cylinderadapted to contain a liquid, and a piston within said cylinder anddividing the interior thereof into a high pressure chamber and a lowpressure chamber, of a switch means comprising a casing mounted uponsaid cylinder and providing two compartments, a diaphragm therebetween,a pair of contacts in one of said compartments and adapted to be closedwhen said piston is moved to create a braking pressure in said highpressure chamber, and an operating member in said other compartment,normally extending into the low pressure chamber of said cylinder, andactuated by said piston to open said contacts when the pressure isrelieved from said high pressure chamber of said cylinder.

3. In a hydraulic brake system, the combination with a closed cylinderadapted to contain a liquid, and a piston within said cylinder anddividing the interor thereof into a high pressure chamber and a lowpressure chamber, of a switch means comprising a casing providing twofluid tight compartments one of which is connected to said low pressurechamber, a pair of normally closed contacts in the other of saidcompartments, and an operating member in the first mentionedcompartment, normally extending into the low pressure chamber of saidcylinder, and actuated by said piston, when the pressure is relieved insaid high pressure chamber, to open said contacts.

4. In a hydraulic brake system, the combination with a closed cylinderhaving a removable wall and adapted to contain a liquid, a piston withinsaid cylinder and dividing the same into a high pressure chamber and alow pressure chamber, and a resilient means acting on said piston toreturn it to a definite position within said cylinder when the pressureis relieved from said high pressure chamber, of a switch means mountedon said wall and comprising a pair of closed contacts, and an operatingmember normally extending from said switch means into the low pressurechamber of said cylinder, and mechanically actuated by said piston uponits return to said definite position to open said contacts.

5. In a hydraulic brake system, the combination with a closed cylinderhaving a removable end wall and adapted to contain a liquid, a pistonmember including a piston dividing said cylinder into a high pressurechamber and a low pressure chamber and including a, piston rod extendingfrom said piston through said removable wall of said cylinder, aflexible sleeve connected at one end to said piston rod and at its otherend to said cylinder to enclose said' removable wall thereof and aresilient means acting on said piston member to return it to a definiteposition when the pressures in said chambers are substantially equal, ofa switch means within said flexible sleeve and comprising a casingmounted on said wall of the cylinder, a flexible diaphragm within saidcasing and dividing the same into two fluid tight compartments one ofwhich is connected to said low pressure chamber, a pair of normallyclosed contacts in the other of said compartments, and an operatingmember in the first mentioned compartment, normally extending into thelow pressure chamber of said cylinder when the liquid in the highpressure chamber is under pressure, and actuated by said piston memberto open said contacts when said piston member is returned to saiddefinite position.

JOHN C. D. JENSEN.

